docs: def intersection(self, other: 'FileLineSet') -> 'FileLineSet':
          """
          Returns a set of file lines that contains the intersection of the lines
          within this set and a given set.
          """
          assert isinstance(other, FileLineSet)
          set_self = set(self)
          set_other = set(other)
          set_union = set_self & set_other
          return FileLineSet.from_list(list(set_union))